Variable showerhead flow by varying internal baffle conductance

ABSTRACT

Apparatuses and techniques for providing for variable radial flow conductance within a semiconductor processing showerhead are provided. In some cases, the radial flow conductance may be varied dynamically during use. In some cases, the radial flow conductance may be fixed but may vary as a function of radial distance from the showerhead centerline. Both single plenum and dual plenum showerheads are discussed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of priority under 35 U.S.C. §119(e) toU.S. Provisional Patent Application No. 61/695,975, entitled “VARIABLESHOWERHEAD FLOW BY VARYING INTERNAL BAFFLE CONDUCTANCE” filed Aug. 31,2012, Attorney Docket No. NOVLP490P/NVLS003770P1, which is incorporatedherein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

Semiconductor processing tools often use components called “showerheads”to distribute process gases, e.g., reactants, across a semiconductorsubstrate during processing. A typical showerhead may include afaceplate that forms one wall of an internal plenum; the faceplate maygenerally be oriented to be parallel to, and facing, a substrate beingprocessed using the showerhead. The faceplate may have a large number ofgas distribution holes arrayed across it, and gases introduced into theinternal plenum may flow through the gas distribution holes and towardsa substrate or substrates processed using the showerhead.

SUMMARY OF THE INVENTION

The systems, methods and devices of the disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein. One innovative aspect of thesubject matter described in this disclosure can be implemented in avariety of ways.

In some implementations, a baffle for a showerhead of a semiconductorprocessing tool may be provided. The baffle may be configured formounting within the showerhead such that a lower plenum volume is formedbetween a bottom surface of the baffle and a faceplate of the showerheadand such that an upper plenum volume is formed between a top surface ofthe baffle and an interior surface of the showerhead. The baffle may beconfigured such that gas that is introduced into the upper plenum volumeduring semiconductor processing operations flows through the baffle,into the lower plenum volume, and then through gas distribution holes inthe faceplate and towards a semiconductor substrate subject to thesemiconductor processing operations. The baffle may include a plate, theplate substantially axially symmetric about a center axis of the bafflewith one side of the plate forming the bottom surface of the baffle. Thebottom surface may be non-parallel to a reference plane normal to thecenter axis in a region of the plate defining the lower plenum volume.The baffle may also include a plurality of through-holes arranged in aradial array, the radial array centered on the center axis.

In some implementations of the baffle, the bottom surface of the platemay define a conical frustum with a cone angle of between 170 and 179.9degrees. In some further implementations of the baffle, the radial arraymay have a diameter of approximately half of the diameter of the plate.

In some implementations of the baffle, the plate may include a lineardisplacement mechanism interface feature configured to interface with amovable end of a linear displacement mechanism. In some furtherimplementations of such a baffle, the linear displacement mechanisminterface feature may be a center post, the center post centered on thecenter axis and protruding from a side of the plate opposite the bottomsurface and in a direction away from the bottom surface.

In some implementations of the baffle, the baffle may be made fromaluminum. In other implementations of the baffle, the baffle may be madefrom a polymeric material.

In some implementations, a showerhead for use in a semiconductorprocessing tool may be provided. The showerhead may include a faceplateand a baffle. The faceplate may include a faceplate bottom surface and afaceplate top surface opposite the faceplate bottom surface. Thefaceplate top surface may partially define a lower plenum volume withinthe showerhead. The showerhead may be configured such that, when theshowerhead is used in a semiconductor manufacturing process, thefaceplate bottom surface is oriented so as to face a semiconductorsubstrate subject to the semiconductor manufacturing process. The bafflemay include a plate with a substantially axially-symmetric shape about acenter axis substantially normal to the faceplate, the plate having abaffle bottom surface facing the faceplate and a baffle top surfacefacing away from the baffle bottom surface. The baffle bottom surfacemay further define the lower plenum volume and the baffle top surfacemay partially define an upper plenum volume. The baffle may also includea plurality of through-holes arranged in a radial array, the radialarray centered on the center axis.

In some implementations, the showerhead may further include a lineardisplacement mechanism configured to displace a center region of theplate by a first distance along the center axis while an edge region ofthe plate is substantially fixed with respect to motion along the centeraxis. In some such implementations, the linear displacement mechanismmay be a computer-controlled linear actuator or screw drive.Alternatively (or additionally), in some such implementations, thelinear displacement mechanism may include a threaded rod configured tobe manually rotated.

In some implementations, the showerhead may further include a centerpost, the center post centered on the center axis and protruding fromthe top surface of the baffle. In some such implementations, the centerpost may protrude through a seal in a back face of the showerhead andthe seal may be configured to permit sliding motion of the center postalong the center axis with respect to the seal. In some suchimplementations, the showerhead may further include a lineardisplacement mechanism configured to displace a center region of theplate by a first distance along the center axis while an edge region ofthe plate is substantially fixed with respect to motion along the centeraxis, the linear displacement mechanism fluidicly isolated from thelower plenum volume and the upper plenum volume by the seal.

In some implementations of the showerhead, the baffle bottom surface maydefine a conical frustum with a cone angle of between 170 and 179.9degrees.

In some implementations of the showerhead, the radial array may have adiameter of approximately half of the diameter of the plate.

In some implementations of the showerhead, a first radial flowconductance may exist between the faceplate and the baffle when theplate is in an undisplaced state, and a second radial flow conductancemay exist between the faceplate and the baffle when the plate isdisplaced by the first distance from the undisplaced state. The secondradial flow conductance may exhibit less radial flow conductance nearthe center axis than the first radial flow conductance.

In some implementations, a showerhead for use in a semiconductorprocessing tool may be provided. The showerhead may include a faceplateand a plurality of gas distribution holes distributed across thefaceplate. The faceplate may include a faceplate top surface partiallydefining a plenum volume of the showerhead and a faceplate bottomsurface configured to be facing a semiconductor substrate during asemiconductor processing operation performed using the semiconductorprocessing tool. The showerhead may also include mechanical displacementmeans for adjusting radial flow conductance across the faceplate topsurface.

In some implementations, a showerhead for use in a semiconductorprocessing tool may be provided. The showerhead may include a faceplate,a plurality of gas distribution holes distributed across the faceplate,and a baffle. The faceplate may include a faceplate top surfacepartially defining a plenum volume of the showerhead and a faceplatebottom surface configured to be facing a semiconductor substrate duringa semiconductor processing operation performed using the semiconductorprocessing tool. The baffle may be offset from the faceplate topsurface, may be substantially centered with respect to the faceplate,and may include a baffle top surface and a baffle bottom surface facingthe faceplate top surface. A separation gap between the baffle bottomsurface and the faceplate top surface may vary with respect to radialposition such that the radial flow conductance between the faceplate topsurface and the baffle bottom surface varies with respect to radialposition.

In some implementations, method for providing a showerhead with avariable radial flow conductance is provided. The method may includeintroducing a process gas into a first plenum volume between a bafflewithin the showerhead and a faceplate of the showerhead, where thebaffle may include a pattern of passages through the baffle throughwhich the process gas is introduced into the first plenum volume, thefaceplate may include a pattern of gas distribution holes configured todeliver gas from the first plenum volume across the surface of asemiconductor substrate, and the baffle may be offset from the faceplateand supported about the baffle's outer edge by the showerhead. Themethod may further include displacing the center of the baffle to induceflexure of the baffle and to produce changes in separation distancebetween the baffle and the faceplate that vary as a function of radialdistance from a center axis of the faceplate.

The method may further include determining the profile of the bafflewhen the baffle is displaced and manufacturing a new baffle thatpossesses the determined profile in an un-displaced state.

In some implementations, a dual-plenum showerhead for use in asemiconductor processing tool may be provided. The showerhead mayinclude a first gas feed tube with a first interior volume and a firstinlet configured to feed gas to the first interior volume and a secondgas feed tube. The first gas feed tube may be concentric with the secondgas feed tube, thereby creating an annular, second interior volumebetween the first gas feed tube and the second gas feed tube. The secondgas feed tube may have a second inlet configured to feed gas to thesecond interior volume, and the first gas feed tube may be of a smallerdiameter than the second gas feed tube. The first interior volume mayalso be fluidly isolated from the second interior volume within thesecond gas feed tube. A dual plenum volume may be substantially definedby an outer wall, the outer wall substantially axially symmetric about afirst axis. The dual plenum volume may be divided into an even number ofsub-volumes by radial barriers substantially extending from the firstgas feed tube to the outer wall. In such an implementation, the firstaxis may be substantially centered on the faceplate, a bottom portion ofthe outer wall may face the faceplate, each sub-volume may have aplurality of plenum gas distribution holes passing through the bottomportion, and every odd sub-volume may be fluidly connected to the firstgas feed tube by a first radial passage, thereby forming a first plenumvolume. Additionally, every even sub-volume may be fluidly connected tothe second gas feed tube by a second radial passage, thereby forming asecond plenum volume, and the first plenum volume may be fluidlyisolated from the second plenum volume between the plenum gasdistribution holes and the first gas inlet.

In some implementations of the dual-plenum showerhead, the sub-volumesmay all be substantially the same size and overall shape.

In some implementations of the dual-plenum showerhead, the sub-volumesmay decrease in height along the first axis as a function of radialposition with respect to the first axis.

In some implementations of the dual-plenum showerhead, the sub-volumesmay increase in height along the first axis as a function of radialposition with respect to the first axis.

In some implementations of the dual-plenum showerhead, there may be atleast 10 sub-volumes.

In some implementations of the dual-plenum showerhead, the showerheadmay further include a faceplate. The faceplate may include a pluralityof gas distribution holes through the faceplate and may be positionedsuch that openings of the gas distribution holes face the plenum gasdistribution holes in the outer wall. In some such implementations, thefaceplate may be offset from the outer wall by a gap.

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale unless specifically indicated as being scaled drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a high-level schematic section view of a typical exampleshowerhead.

FIG. 2A depicts a conceptual section view of an example of a showerheadconfigured to provide variable radial flow conductance within theshowerhead using a flexible baffle.

FIG. 2B depicts a conceptual section view of the example showerhead fromFIG. 2A with the flexible baffle in a displaced condition.

FIG. 3A depicts an isometric view of an example of a showerheadconfigured to provide variable radial flow conductance.

FIG. 3B depicts an isometric exploded view of the example showerheadfrom FIG. 3A.

FIG. 3C depicts a side section view of the example showerhead from FIG.3A.

FIG. 3D depicts a side section view of the example showerhead from FIG.3A with the baffle in a displaced condition.

FIG. 4 depicts a flow diagram for one example technique for producing astatic variable radial flow conductance showerhead baffle.

FIG. 5 depicts a flow diagram for one example open-loop technique forcontrolling a variable radial flow conductance showerhead.

FIG. 6 depicts a flow diagram for one example closed-loop technique forcontrolling a variable radial flow conductance showerhead.

FIG. 7A depicts an isometric view of a dual-plenum showerhead configuredto provide variable radial flow resistance within the showerheadplenums.

FIG. 7B depicts an isometric view of the dual-plenum showerhead of FIG.7A with the backplate removed and with a portion of the outer wallremoved to allow viewing of the radial barriers.

FIG. 8A depicts an isometric exploded view of the dual-plenum showerheadof FIG. 7A.

FIG. 8B shows an isometric detail view of the first gas feed tube shownin FIG. 8A.

FIG. 9 depicts an isometric, multi-section cutaway view of thedual-plenum showerhead of FIG. 7A.

FIG. 10A depicts a side view of the dual-plenum showerhead of FIG. 7A.

FIG. 10B depicts a section view of the dual-plenum showerhead of FIG.10A.

FIG. 11A depicts one of the two plenum volumes of a dual-plenumshowerhead.

FIG. 11B depicts a complementary plenum volume to the plenum volumeshown in FIG. 11A.

FIG. 11C depicts the dual plenum volume including both plenum volumesshown in FIGS. 11A and 11B.

FIGS. 3A-3D and 7A-11C are scaled drawings, although the drawing scalemay vary from Figure to Figure (the proportions within each Figure arestill to-scale, however).

DETAILED DESCRIPTION

Examples of various implementations are illustrated in the accompanyingdrawings and described further below. It will be understood that thediscussion herein is not intended to limit the claims to the specificimplementations described. On the contrary, it is intended to coveralternatives, modifications, and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claims.In the following description, numerous implementation-specific detailsare set forth in order to provide a thorough understanding of thepresent invention. The present invention may be practiced without someor all of these implementation-specific details. In other instances,well-known process operations have not been described in detail in ordernot to unnecessarily obscure the present invention.

FIG. 1 depicts a high-level schematic section view of a typical exampleshowerhead. Showerhead 100 may include a faceplate 102 with a faceplatetop surface 138 and a faceplate bottom surface 136. A pattern of gasdistribution holes 112 may allow for fluidic communication between aplenum volume 108 formed within the showerhead 100 and a processingregion interposed between the faceplate 102 and a semiconductorsubstrate 104. The semiconductor substrate 104 may be supported by asubstrate support 106. A gas inlet 110 may allow for semiconductorprocessing gases to be introduced to the plenum volume 108 and thendistributed across the semiconductor substrate 104 via the gasdistribution holes 112. The showerhead 100, semiconductor substrate 104,and substrate support 106 may be housed within a semiconductorprocessing chamber or reactor (not shown) that is part of asemiconductor processing tool (also not shown).

While the typical showerhead 100 of FIG. 1 is most similar to a“chandelier” type showerhead, e.g., the showerhead may be suspended fromthe top of a semiconductor processing chamber by a stem 144, thetechniques and mechanisms discussed herein may, in addition to beingused in chandelier-type showerheads, be used in “flush-mount” typeshowerheads, e.g., showerheads that, instead of being supported by astem near the center of the showerhead, are supported about theperiphery of the showerhead and that may form part of the roof of asemiconductor processing chamber. This disclosure is to be understood toapply to variable flow conductance mechanisms suitable for use witheither type of showerhead.

During operation of a typical showerhead, the process gas that isdistributed across the surface of a semiconductor substrate may bedistributed in a non-uniform manner due to the internal geometry of theshowerhead, the manner in which the process gas is routed to the gasdistribution holes, etc. Various techniques have been used to tune thedistribution of such process gases, including varying the arrangement ofgas distribution holes across the faceplate, introducing “dual zone”showerheads where the gas distribution holes are separated into a centergrouping and an annular outer grouping, each fed by a different plenumand supplied with process gases at different concentrations and/or flowrates, and by adjusting the size of the gas distribution holes.

Presented herein are techniques and mechanisms for adjusting the amountof process gas that flows out of the gas distribution holes of ashowerhead by varying the radial flow conductance of the process gaseswithin the showerhead. Such techniques and mechanisms allow for the flowrates of process gases delivered across a semiconductor substrate to beprecisely tuned or adjusted without requiring re-machining of showerheadcomponents, and, in some implementations, allow for such flow rates tobe adjusted mid-process. This allows for enhanced uniformity across thesemiconductor substrate, e.g., more uniform deposition layer thicknessor etch removal thickness.

FIG. 2A depicts a conceptual section view of an example of a showerheadconfigured to provide variable radial flow conductance within theshowerhead using a flexible baffle. A showerhead 200 is shown with afaceplate 202 (the faceplate 202 is shown as an integral part of theshowerhead 200, but, in practice, may be a removable faceplate or may bea separate part welded onto the showerhead main body). The showerhead200 may also include a baffle 214 that divides the internal volume ofthe showerhead 200 into two volumes: a lower plenum volume 218 and aupper plenum volume 220. The baffle 214 may be supported about its outerperimeter by the showerhead 200. Such support may, for example, be asimple support, a cantilevered (clamped on top and bottom by theshowerhead 200 or welded/bonded to the showerhead 200) support, or beprovided by, for example, threaded fasteners that secure the baffle 214to the showerhead 200.

The faceplate 202 may have a faceplate bottom surface 236 and afaceplate top surface 238. The faceplate bottom surface 236 may beconfigured to face towards a substrate (not shown) processed using theshowerhead 200. The faceplate top surface 238, along with a bafflebottom surface 224, may be configured to partially (or wholly) definethe lower plenum volume 218. A baffle top surface 222 maycorrespondingly partially define the upper plenum volume 220. The upperplenum volume 220 may also be partially defined by an interior surface226 of the showerhead 200.

Process gas may be introduced into the upper plenum volume 220 via oneor more gas inlets 210. The process gas may then flow through the baffle214 through, for example, a radial array of through-holes 230 locatedapproximately mid-diameter on the baffle 214. It is to be understoodthat other arrangements of through-holes 230 (including other shapes ofthrough-holes) may be used as well, although such arrangements maygenerally be configured to produce a gas flow into the lower plenumvolume that is substantially axially symmetric about a center axis 228of the showerhead 200. For example, in some implementations, the radialarray of through-holes 230 may be located near the perimeter of thebaffle rather than at approximately the mid-diameter.

In the implementation shown, the baffle 214 has the general shape of acircular plate with a slight taper on the baffle bottom surface 224,which gives the baffle bottom surface 224 the appearance of a veryshallow, conical frustum. Due to this slight taper, the separationdistance between the faceplate top surface 238 and the baffle bottomsurface 224 decreases with radial position as the point of separationdistance measurement approaches the center axis 228. This has the effectof reducing the cross-sectional area through which gas flowing radiallytowards the center axis 228 and between the faceplate top surface 238and the baffle bottom surface 224 may flow, i.e., reducing the flowconductance or increasing the flow resistance experienced by the processgas as it flows towards the center axis 228.

Other contours may be used for the baffle bottom surface 224 as well,including simple, flat profiles that do not reduce the separationdistance between the faceplate top surface 238 and the baffle bottomsurface 224. The baffle may also be contoured along the top surfaceinstead of, or in addition to, the bottom surface 224, and the contoursused may also be non-linear contours (as opposed to linear, taperedcontours).

Regardless of what profile is used for the baffle bottom surface 224,the resulting radial flow conductance may be altered by applying a forceto a center region of the baffle top surface 222 and causing the baffle214 to flex in a substantially axially-symmetric manner. This may havethe effect of causing the separation distance between the faceplate topsurface 238 and the baffle bottom surface 224 to change by varyingamounts in the radial direction. The change in separation distance maybe most acute along the center axis 228, and may be minimal ornon-existent at the edge of the baffle 214, i.e., where the baffle 214is supported by the showerhead 200.

For example, in FIG. 2A, the baffle 214 is shaped to provide a radialflow conductance in the un-flexed state that causes a greater amount ofprocess gas to be delivered through the center region of the faceplate202, as indicated by the arrows/flow paths of greater length towards thecenter region of the faceplate 202 as compared with the arrows/flowpaths of shorter length towards the perimeter of the faceplate 202.

In FIG. 2B, the center region of the baffle 214 has been displacedtowards the faceplate 202 by a distance roughly corresponding to thethickness of the baffle 214 (this distance may not be representative ofthe actual amount of deflection that may be used; for example, thedisplacement may be on the order of thousandths or hundredths of aninch). For reference, the outline of the un-displaced baffle is shownwith a dashed line. This may cause the radial flow conductance betweenthe faceplate top surface 238 and the baffle bottom surface 224 todecrease substantially closer to the center axis 228. In turn, this maycause a greater amount of process gas to be delivered through the gasdistribution holes 230 closer to the edge region of the faceplate 202than is delivered through the gas distribution holes 230 near the centerof the faceplate 202. Again, this flow pattern is illustrated by the useof arrows/flow paths of varying lengths across the span of the faceplate202.

Such displacement of the baffle 214 may be effected through a lineardisplacement mechanism such as, for example, a screw-driven linearactuator, a cam- or wedge-actuator, or a hydraulic actuator. Otherlinear displacement mechanisms also may be used if appropriate. Suchlinear displacement mechanisms may, in general, exhibit a high degree ofprecision and accuracy in terms of the linear displacement they effect,and may be capable of very small displacements, e.g., on the order ofthousandths of an inch.

The displacement force may be delivered to the baffle 214 through alinear displacement mechanism interface feature such as, for example,center post 234. The center post 234 may, for example, protrude througha seal (not shown) in the backplate 246 of the showerhead 200. The sealmay provide a sliding seal interface between the backplate 246 and thecenter post 234 that fluidly isolates whatever linear displacementmechanism is used to displace the baffle 214 from the process gasespresent in the upper plenum volume. The seal may also serve to isolatethe lower plenum volume 218 and the upper plenum volume 220 from anycontaminants that may be produced by the linear displacement mechanismand the interaction of the linear displacement mechanism with the lineardisplacement mechanism interface feature, e.g., lubricants, dust, etc.

In some implementations, the baffle top surface may be connected, forexample, to the showerhead by a bellows device located within anypattern of through-holes in the baffle. The bellows device may allow thecenter of the baffle to flex relative to the showerhead while keepingthe center of the baffle, as well as any linear displacement mechanismcomponents and linear displacement mechanism interface features,isolated from the upper plenum volume and any process gases containedtherein.

In some implementations, the linear displacement mechanism interfacefeature may be configured to transmit only compressive axial force tothe baffle. For example, the baffle (or center post) may include arecess or other receptacle configured to receive, for example, the endof a linear screw actuator shaft. When the baffle is elasticallydeflected by a force applied using the linear displacement mechanism,the baffle will exert a corresponding force in the opposite directionand will maintain a contact relationship with the linear displacementmechanism. When the linear displacement mechanism force is removed, thebaffle may then return to its unstressed (or less-stressed) state.

In other implementations, the linear displacement mechanism interfacefeature may be configured to transmit both compressive and tensile forceto the baffle. Such implementations may allow for the baffle to be“pulled away” from the faceplate as well as “pushed towards” thefaceplate. This may provide the showerhead with additional radial flowconductance tuning flexibility. Such interface features may, forexample, include receptacles with positive capture features, e.g.,ball-and-socket joints, welds, etc., that transmit both types of forceto the baffle.

The linear displacement mechanism may be powered or unpowered. A poweredlinear displacement mechanism may be used to actively control the radialflow conductance during semiconductor processing. For example, thelinear displacement mechanism may be a precision electromechanicallinear screw drive coupled to a controller that is either incommunication with a controller for a semiconductor processing tool thathouses the showerhead or that is part of such a controller. Thecontroller may be configured to engage (or disengage) the lineardisplacement mechanism at various points during a semiconductor processso as to dynamically alter the flow characteristics of process gasesthrough the showerhead. For example, a semiconductor processingtechnique may include delivering two different process gasessequentially. The first process gas may require more delivery towardsthe center of the semiconductor substrate, and the second process gasmay require more delivery towards the perimeter of the substrate. Byengaging the linear displacement mechanism to displace the baffletowards the faceplate in between the delivery of the first and secondprocess gases, the radial flow conductance may be shifted such that thedesired flow patterns are produced. This may be done without swappingout showerhead faceplates or using multiple showerheads, and in a matterof seconds or less.

Unpowered linear displacement mechanisms may also be used. Such lineardisplacement mechanisms may allow for a human operator to preciselyadjust the degree of radial flow conductance through the use of handtools, e.g., a spanner, wrench, or other equipment. Unpoweredimplementations may not allow for in-process changes of flowconductance, but may allow for a human operator to tune a particularshowerhead flow profile as needed for a particular process, and thenmake periodic adjustments as needed to account for showerheaddegradation or re-purposing for different semiconductor processes.

In some implementations, showerheads with manually-driven lineardisplacement mechanisms may be provided that are configured to beretrofitted with a powered linear displacement mechanism (and/orcontroller).

A second example implementation of a showerhead that is configured toprovide variable radial flow conductance is discussed below. FIG. 3Adepicts an isometric view of an example of a showerhead configured toprovide variable radial flow conductance. FIG. 3B depicts an isometricexploded view of the example showerhead from FIG. 3A.

The showerhead 300 shown is a flush-mount showerhead, and includes adouble-C shaped heater loop channel 342 that is configured to receive aresistive heater element (not shown). Also visible is an insert 348,which may be used to provide, for example, process gas inlets (notshown) and a feed-through for a center post 334 that interfaces with alinear displacement mechanism 332. The showerhead 300 includes a backplate 346 and a faceplate 302, as well as a baffle 314. The baffle 314may include a plate 316, a center post 334, and a circular array ofthrough-holes 330. The circular array of through-holes 330 may belocated approximately mid-diameter on the plate 316. The baffle 314 maybe interposed between the back plate 346 and the faceplate 302. Thefaceplate 302 may include a plurality of gas distribution holes 312. Inthe pictured implementation, the gas distribution holes 312 are arrayedin a square grid with 0.3″ hole spacing; the gas distribution holes 312in this implementation are approximately 0.02″ in diameter. In otherimplementations, other sizes and patterns of gas distribution holes maybe used, e.g., spiral patterns, variable density patterns, concentriccircular patterns, etc.

The gas distribution hole pattern used may be selected based on thesteady-state gas distribution that is desired, i.e., when the gaspressure within the lower plenum volume reaches equilibrium. Thevariable radial flow conductance aspects of implementations discussedherein may be primarily used to affect the transient gas distribution inthe lower plenum volume, i.e., when the gas pressure has not yet reachedequilibrium within the lower plenum volume. Thus, the tunable radialflow conductance aspects of the implementations discussed herein may beused to tailor the transient gas flow regimes within the showerhead, andthe gas distribution hole patterns/sizes may be used to tailor thesteady-state gas flow regimes within the showerhead. For processes ofshort duration, such as thin-film deposition, the transient domain maybe a more significant portion of the overall process interval and ashowerhead with tunable radial flow conductance may provide asignificant uniformity boost.

It is to be understood that while the focus of this discussion has beenon using a variable radial flow conductance showerhead to promote moreprocess uniformity, in some situations, it may be desirable todeliberately alter the radial flow conductance to promote less processuniformity, at least within a particular semiconductor processing step.For example, a semiconductor wafer may, at the start of a processingstep, already possess non-uniform features. To correct suchnon-uniformity, a variable radial flow conductance showerhead may beconfigured to distribute gas in a non-uniform manner that produces anon-uniform layer deposition. This non-uniform layer deposition may,however, help “even out” the non-uniform thickness of a semiconductorsubstrate, and result in a substrate that is more uniform in overallappearance. Due to the large degree of tunability in a variable radialflow conductance showerhead, such strategies may be a practical path toaddressing such substrate issues.

FIG. 3C depicts a side section view of the example showerhead from FIG.3A. FIG. 3D depicts a side section view of the example showerhead fromFIG. 3A with the baffle in a displaced condition. As can be seen,relatively little change in separation distance between the faceplate302 and the baffle 316 may be observed in response to the displacementof baffle 314 with respect to the faceplate 302.

In the implementation pictured in FIGS. 3A through 3D, for example, theseparation distance between the baffle bottom surface 324 near the outeredge of the baffle and the faceplate top surface 338 may remain at asubstantially fixed value, e.g., 3.75 mm, in both the displaced and theun-displaced state. The separation distance between the baffle bottomsurface 324 and the faceplate top surface 338 near the center axis 328may change when the baffle 314 is transitioned from the un-displacedstate to the displaced state, e.g., from a distance of approximately3.75 mm to a distance of 2.75 mm. The baffle 314 shown in this examplemay be approximately 13″/336 mm in diameter, and the through-holes 330may be approximately 0.15″/3.8 mm in diameter and may be arranged on a6.375″/162 mm diameter hole pattern centered on the center axis 328. Thebaffle bottom surface 324 may, as shown in FIGS. 3C and 3D, form aconical frustum with approximately a 178 degree cone angle.

The baffles described herein may be manufactured from a variety ofmaterials, depending on the particular requirements of the environmentsto which they are to be subjected. Baffles may, for example, be madefrom aluminum, titanium, stainless steel, and possibly, in some cases,ceramics. Other materials that may be used for baffles include Teflon,polyimides, and other polymeric materials. In general, the material usedfor a baffle may be selected for resistance to attack by process gasesused, tolerance of temperatures experienced within the showerhead, andelasticity sufficient to allow for flexure of the baffle withoutbreakage. Due to the small displacements that may be imposed on thecenter of the baffles, brittle materials, such as ceramics, maynonetheless be suitable for use in some baffle designs. In someimplementations, elements of the baffle may be made from differentmaterials. For example, the baffle plate may be made from a polymer, andthe center post, if used, may be made from aluminum.

In some configurations, a center post may be used that also acts as agas inlet. For example, the top of the center post may be configured tomate with a gas supply line, and the center post may be hollow and havea plurality of ports about its circumference within the upper plenumvolume. Process gas may be flowed into the gas inlet, through the centerpost, and into the upper plenum volume via the ports.

While the above discussion has focused on showerheads that feature atunable radial flow conductance across the faceplate of the showerheadusing a flexible baffle, some implementations may feature a staticbaffle that is contoured to provide a particular radial flowconductance. For example, in many semiconductor processes, once theoptimum process parameters are established, it may be desirable tominimize the number of potential sources of variability. Thus, it may beundesirable to include a showerhead with a flexible baffle since thismay be a source of variability. During development of such processes,however, a showerhead with a flexible baffle may be desired so as toallow for easy iterative testing of various baffle configurations. Insuch implementations, a showerhead with a flexible baffle and a tunableradial flow conductance may be used to “dial in” a desired radial flowconductance profile. Once a particular radial flow conductance profileis identified as optimal or desired, measurements of the displaced stateof the baffle may be taken and used, for example, to manufacture abaffle that, in the unstressed state, has the same bottom surfacecontour as the bottom surface contour of the flexible baffle in thedisplaced state, i.e., stressed state, that produced the desired radialconductance profile. This pre-shaped baffle may then be produced inlarge quantities and installed in the equipment that will be performingthe semiconductor process of interest. This eliminates the need toindividually adjust each baffle in each semiconductor tool.

FIG. 4 depicts a flow diagram for one example technique for producing astatic variable radial flow conductance showerhead baffle. Afterbeginning in block 402, the technique involves measuring flow orsubstrate uniformity resulting from the performance of a particularsemiconductor processing operation. In block 406, the measureduniformity (or lack thereof) is analyzed to determine whether the baffleneeds to be displaced further or displaced less (or not at all). Such adetermination may be made according to the general guidelines discussedherein. If the measured uniformity is not within acceptable levels inblock 408, the technique may return to block 404 for further refinementof the baffle displacement. If the measured uniformity is withinacceptable levels in block 408, the technique may next involve obtaininga profile of the deflected baffle in block 410. In block 412, a newbaffle may be machined (or otherwise produced) that features theobtained profile when the baffle is in a substantially unstressedcondition. In block 414, the new baffle may be installed in asemiconductor processing tool. The technique ends in block 416, afterwhich the new baffle may be used during semiconductor processingoperations involving the semiconductor processing tool.

The above discussion has focused primarily on showerhead implementationswith internal volumes that are all in fluidic communication with eachother within the showerhead. Various aspects of the tunable or static,tuned variable radial flow conductance technologies discussed above mayalso be implemented in showerheads that may be used to distribute twogases across a semiconductor substrate while keeping these gases fluidlyisolated from each other within the showerhead, or at least isolatedfrom each other within most of the showerhead. Such showerheads, whichare often referred to as “dual plenum” showerheads (not to be confusedwith the lower plenum volume and the upper plenum volume formed by theflexible baffle showerheads discussed above), may feature a dual plenumvolume bounded by an outer wall that may be partitioned into a firstplenum volume and a second plenum volume by a series of radial barriers.The first plenum volume may be connected to a first process gas sourceand be used to distribute the first process gas across a semiconductorsubstrate using a plurality of plenum gas distribution holes passingfrom the first plenum volume through the outer wall. The second plenumvolume may be connected to a second process gas source and be used todistribute the second process gas source across the semiconductorsubstrate in a similar manner.

FIG. 7A depicts an isometric view of a dual-plenum showerhead configuredto provide variable radial flow resistance within the showerheadplenums. In FIG. 7A, a showerhead 700 is depicted. The showerhead 700includes a coned backplate 750 (the coned aspect is visible in laterFigures), which may include a heater loop channel 742. A first gas feedtube 752 may be coaxially located with respect to a second gas feed tube754, thus creating an annular volume between the first gas feed tube 752and the second gas feed tube 754 that is capped off near the protrudingend of the first gas feed tube 752 or the second gas feed tube 754. Thefirst process gas may be fed into a first interior volume of the firstgas feed tube 752 via a first inlet or inlets 756. The second processgas may be fed into a second interior volume, e.g., the annular volumebetween the first gas feed tube 752 and the second gas feed tube 754,via a second inlet or inlets 758.

FIG. 7B depicts an isometric view of the dual-plenum showerhead of FIG.7A with the backplate removed and with a portion of the outer wallremoved to allow viewing of the radial barriers. As can be seen, beneaththe coned backplate 750 lies a dual plenum volume that is containedwithin an outer wall 760. The outer wall 760 may, as in thisimplementation, be a substantially axially symmetric, thin-wall vesselthat substantially spans the width of the showerhead 700. The outer wall760 may define the outer boundaries of the dual plenum volume. The outerwall 760 may also house a number of radial barriers 762 that extendsubstantially from the outermost interior surface of the outer wall 760towards the center of the dual plenum volume.

The radial barriers 762 may define an even-numbered, radial array ofsub-volumes. Each sub-volume may include a pattern of plenum gasdistribution holes 764 that pass from the sub-volume, through the outerwall, and in the direction that a wafer would lie during semiconductorprocessing. In the example, shown, there are a total of 16 sub-volumes,although, in other implementations, the number of sub-volumes may rangebetween 10 and 24 (in even increments). In theory, there may be no upperlimit on the number of sub-volumes, although the thickness of the radialbarriers 762 may, in practice, limit the number of sub-volumes.

FIG. 8A depicts an isometric exploded view of the dual-plenum showerheadof FIG. 7A. The outer wall 760 and the components within it are shownwith hidden lines visible to allow the radial barriers 762 to be easilyseen. In this implementation, the second gas feed tube 754 is joined tothe outer wall 760 at the base and the first gas feed tube 752, whenassembled, may be slid into the second gas feed tube 754 and then brazedinto place. This may allow the mating surfaces of the first gas feedtube 752, the second gas feed tube 754, and the radial barriers 762 tobe fused together in a gas-impermeable manner, thus fluidly isolatingthe first interior volume and the second interior volume from each otherwithin the showerhead.

FIG. 8B shows an isometric detail view of the first gas feed tube shownin FIG. 8A. As can be seen, the base of the first gas feed tube 752 mayhave a stepped-up diameter that substantially matches the internaldiameter of the second gas feed tube 754. A radial array of longitudinalgrooves in the stepped-up diameter region may be arranged about thecenter axis of the first gas feed tube 752. These grooves may allow gasthat is present in the second interior volume to flow out of the secondinterior volume, into the stepped region, and then in a radial directionaway from the first gas feed tube 752. The grooves are not deep enough,however, to breach the inner wall of the first gas feed tube 752.

A similar array of longitudinal slots may also be present in the steppedup region. The longitudinal slots may pierce the inner wall of the firstgas feed tube 752, thus allowing gas that is present in the firstinterior volume to flow out of the first interior volume, through thestepped region, and in a radial direction away from the first gas feedtube 752. The longitudinal slots may form a radial array of first radialpassages 766, and the longitudinal grooves may for a radial array ofsecond radial passages 768. Other configurations of parts may be used aswell to produce substantially the same result, i.e., a two-gas feedsystem that, at one end, distributes the two different gases used inradial directions and in an alternating, segregated manner, and thisdisclosure should not be viewed as being limited to the particularimplementation shown in the Figures.

Also visible in FIG. 8A is faceplate 702, which may be similar to thefaceplate 202 discussed earlier. However, it is to be understood that,in some implementations, the bottom surface of the outer wall 760 mayserve the same purpose as the faceplate 702, and a separate faceplate702 may therefore be unneeded.

FIG. 9 depicts an isometric, multi-section cutaway view of thedual-plenum showerhead of FIG. 7A. In FIG. 9, the showerhead 700 isshown with various portions sectioned away to allow for easier viewingof the internal structures of the showerhead 700. For example, awedge-shaped section of the first gas feed tube 752 has been cut awayfrom the top of the first gas feed tube 752 to a point just above thestepped region. The remaining parts have been sectioned along the axialmidplanes of the showerhead to a point approximately halfway along thelongitudinal slots/grooves in the stepped region. A further wedge-shapedsection of the remaining components has also been removed to allow forfurther interior viewing.

In FIG. 9, white arrows depict notional gas flow of the first processgas through the first gas feed tube 752, through the longitudinal slots,and into the “odd” sub-volumes 770. Black arrows depict notional gasflow of the second process gas through the second gas feed tube 754,through the longitudinal grooves, and into the “even” sub-volumes 772.Once introduced into the odd sub-volumes 770 and the even sub-volumes772, the respective gases may flow through the sub-volumes and towardsthe periphery of the outer wall 760. The radial flow conductance of thegases may be tuned, for example, to offset the potential increase inflow conductance due to the expanding circumferential width of thesub-volumes as one traverses the sub-volumes towards the outer wall 760.This may be accomplished by sloping the outer wall 760 so that thesub-volumes decrease in height as the distance to the outer wall 760decreases. This increases the radial flow resistance due to the heightof the sub-volumes at the same time that the radial flow resistance dueto the width of the sub-volumes may be decreasing. Of course, otherconfigurations of outer wall may be used as well, depending on the gasflow behavior desired. For example, the outer wall 760 could, instead,increase in height as one approaches the outer perimeter of the outerwall 760. Non-linear outer wall profiles may also be used to adjust thegap, and thus the radial flow conductance, between the portions of theouter wall 760 forming the “top” and “bottom” of the dual plenum volume774.

It is to be understood that an “even” or “odd” sub-volume mayalternatively be used to refer to a grouping of adjacent sub-volumesthat are all used to distribute the same gas. For example, in someimplementations, each sub-volume may be further subdivided intosub-sub-volumes, or there may be two sub-volumes adjacent to each otherthat may, in effect, be viewed as a single sub-volume since they areboth fed from the same gas feed tube.

As depicted in FIG. 9, the bottom of the dual plenum volume 760featuring the plenum gas distribution holes 764 is in contact with thefaceplate 702. In such implementations, the plenum gas distributionholes 764 may be distributed in a pattern corresponding to the patternof gas distribution holes 712 in the faceplate 702. While such amatching pattern is not shown in the implementation depicted in FIG. 9,it is to be understood that such an implementation is within the scopeof this disclosure. Additionally, as discussed previously, someimplementations may do away with the faceplate 702 entirely, and simplyuse the bottom portion of the outer wall 760 to provide gas distributionfunctionality.

In some other implementations, however, the bottom of the outer wall 760may be offset from the faceplate 702 by a gap, providing a space inbetween the faceplate 702 and the dual plenum volume 774 within whichthe gases exiting the odd sub-volumes 770 and the even sub-volumes 772may pre-mix prior to passing through the gas distribution holes 712 inthe faceplate 702 and towards a wafer being processed using theshowerhead 700. Such an implementation is not depicted in the Figures,but is to be understood to be within the scope of this disclosure.

Such pre-mixing may result in a more uniform gas distribution across awafer that is being processed using the showerhead 700. Dual plenumshowerheads are typically used to segregate two precursors and preventpremature intermixing and reaction of the precursors. When suchprecursors intermix, condensation may be formed under certainenvironmental conditions, e.g., sub-dew point conditions. While formingsuch condensation on the wafer may be desirable, it may be undesirableif the condensation forms within the showerhead 700. Heating theshowerhead 700 via a heater element routed in the heater loop channel742 may elevate the temperatures within the dual plenum volume to apoint above the dew point, preventing premature condensation.

FIG. 10A depicts a side view of the dual-plenum showerhead of FIG. 7A.FIG. 10B depicts a section view of the dual-plenum showerhead of FIG.10A. As can be seen in the section view, the two gases are distributedin a repeating, interleaved radial pattern.

FIG. 11A depicts a second plenum volume 782 including the evensub-volumes 772 and the second interior volume 778. It is to beunderstood that the second plenum volume 782 shown is not actually acomponent, but an internal “free” volume defined by the variouscomponents described in FIGS. 7A through 10B. The second plenum volume782 represents the volume, for example, within which the second gas mayfluidly flow within the dual plenum volume 774.

FIG. 11B depicts a first plenum volume 780. It is also to be understoodthat the first plenum volume 780 shown is not actually a component, butan internal “free” volume defined by the various components described inFIGS. 7A through 10B. The first plenum volume 780 represents the volume,for example, within which the first gas may fluidly flow within the dualplenum volume 774.

FIG. 11C depicts the dual plenum volume including both plenum volumesshown in FIGS. 11A and 11B. In this Figure, the first plenum volume 780and the second plenum volume 782 are positioned according to theirrelative positioning within the dual plenum volume 774. As can be seen,the first plenum volume 780 and the second plenum volume 782 areintermeshed with one another but do not intersect one another.

As discussed above, some implementations may feature a powered,actively-controlled linear displacement mechanism controlled by acontroller. The controller may include a specially-programmed computingdevice, e.g., a device that functions according to software instructionsstored on/in a machine readable medium, e.g., on a hard disk, memorydevice, CD or DVD, network storage system, etc. Such instructions may beexecutable by one or more processors of the computing device and may beused to cause the linear displacement mechanism to displace the centerof the baffle by various amounts during various stages of asemiconductor process.

In some implementations, the controller may operate in an open-loopmanner, e.g., the controller may be pre-programmed with defineddisplacement distances for the linear displacement mechanism, eachassociated with a different phase of a semiconductor process, and maycontrol the motion of the linear displacement mechanism according tothese defined distances.

FIG. 5 depicts a flow diagram for one example open-loop technique forcontrolling a variable radial flow conductance showerhead. The techniquemay begin in block 502. In block 504, displacement data, e.g., a defineddisplacement distance, may be referenced by a controller. In block 506,a linear displacement mechanism may be actuated to cause the baffle inthe variable radial flow conductance showerhead to be displaced by thedefined displacement distance. It should be noted that the displacementdistance, while perhaps provided with respect to any of severalcoordinate frames, ultimately defines, either directly or indirectly,the separate distance between the bottom surface of the baffle and thetop surface of the faceplate. In block 508, a determination is made asto whether further displacement is needed. For example, if a latersemiconductor processing phase requires a different displacement, thetechnique may return to block 504 and new displacement data may bereferenced. If further displacement adjustment is not needed, thetechnique ends in block 510. This technique may be repeatedly performedfor successive substrates processed in a semiconductor processing toolequipped with the variable radial flow conductivity showerhead.

In some other implementations, however, the controller may operate in aclosed-loop manner, e.g., the controller may receive feedback regardingprocess variability during the semiconductor process, or periodically inbetween semiconductor processes, and adjust the amount of lineardisplacement used during various stages of the semiconductor processaccordingly. For example, measurements of gas distribution across thefaceplate may be taken and if the gas distribution is biased towards theoutside of the wafer, the radial flow conductance within the showerheadmay be increased towards the center of the faceplate. If the gasdistribution is biased towards the center of the wafer, the radial flowconductance within the showerhead may be decreased towards the center ofthe faceplate.

Another technique that may be used is to measure the gap distancedynamically, e.g., using an optical vacuum feed-through and a laser gapmeasurement device, and then adjust the displacement of the baffle suchthat the measured gap distance approaches a desired value. Such desiredgap values may be determined experimentally.

Another technique may involve evaluating semiconductor substratesprocessed using the variable radial flow conductance showerhead wafersfor non-uniformity, e.g., in-line metrology, and then adjusting theradial flow conductance of the showerhead based on measurementsperformed on the semiconductor substrate. Thus, if a semiconductorsubstrate processed using such a showerhead exhibits a non-uniformity,the radial flow conductance may be adjusted as needed for subsequentsemiconductor substrate processing operations. This will not address thenon-uniformity in the evaluated substrate, but may improve theuniformity of subsequently-processed substrates. Such evaluation andvariable radial flow conductance adjustment may be performed at regularintervals, resulting in a semi-closed-loop feedback system.

FIG. 6 depicts a flow diagram for one example closed-loop technique forcontrolling a variable radial flow conductance showerhead. The techniquemay begin in block 602, and may involve processing a semiconductorsubstrate with a variable radial flow conductance showerhead set to aparticular baffle displacement (or baffle/faceplate separationdistance). In block 606, an evaluation of process non-uniformity (oruniformity) may be made. This, for example, may involve in-situmeasurement of gas flow distribution, or in-line metrology measurementsof semiconductor substrate layers. In block 608, a determination may bemade as to whether the measured non-uniformity or uniformity fallsoutside of desired parameters. If so, the baffle/faceplate separationdistance may be adjusted, accordingly, in block 614 for a followingsemiconductor substrate (or, for in-situ measurements, for thesemiconductor substrate currently being processed). After adjustment (orif no adjustment is needed), the technique may proceed to block 610,where a subsequent semiconductor substrate may be processed. In the caseof in-situ measurement, the technique may optionally return to block606, where a further measurement may be taken and further adjustmentsmay be made. The technique may end in block 612.

The variable radial flow conductance showerheads described hereinabovemay be used in conjunction with lithographic patterning tools orprocesses, for example, for the fabrication or manufacture ofsemiconductor devices, displays, LEDs, photovoltaic panels and the like.Typically, though not necessarily, such tools/processes will be used orconducted together in a common fabrication facility. Lithographicpatterning of a film typically comprises some or all of the followingsteps, each step enabled with a number of possible tools: (1)application of photoresist on a workpiece, i.e., substrate, using aspin-on or spray-on tool; (2) curing of photoresist using a hot plate orfurnace or UV curing tool; (3) exposing the photoresist to visible or UVor x-ray light with a tool such as a substrate stepper; (4) developingthe resist so as to selectively remove resist and thereby pattern itusing a tool such as a wet bench; (5) transferring the resist patterninto an underlying film or workpiece by using a dry or plasma-assistedetching tool; and (6) removing the resist using a tool such as an RF ormicrowave plasma resist stripper.

In some implementations, a variable radial flow conductance showerheadmay be used with flowable oxide processes. In existing flowable oxideprocesses, a dual-zone showerhead is sometimes used to provide differentflow characteristics near the center of the faceplate as compared withan annular region about the center region of the faceplate. Dual zoneshowerheads may feature an annular wall inside of the showerhead thatmates with the top surface of the faceplate. The annular wall dividesthe showerhead internal volume into a central plenum (within the annularwall) and an annular plenum (outside of the annular wall). Differentprocess gas feeds may supply the central plenum and the annular plenum,and each zone of the dual zone showerhead may be fed from gasdistribution holes from a different one of the plenums. A dual zoneshowerhead may, however introduce a localized discontinuity in thetransition region between the two zones, however, due to the suddenchange in process gas properties that may result from the presence ofthe annular wall. A variable radial flow conductance showerhead, bycontrast, may avoid such localized discontinuities since the lowerplenum volume may be continuous across the top surface of the faceplate.

In some implementations, a variable radial flow conductance showerheadmay be installed in a reactor and linked to a system controller havinginstructions for controlling process operations. The system controllerwill typically include one or more memory devices and one or moreprocessors configured to execute the instructions so that the apparatuswill perform various semiconductor fabrication processes.Machine-readable media containing instructions for controlling processoperations may be coupled to the system controller. The processors mayinclude a CPU or computer and may include or be communicativelyconnected with one or more analog and/or digital input/outputconnections, stepper motor controller boards, etc. The systemcontroller, for example, may be configured to, in addition tocontrolling radial flow conductance in the showerhead via lineardisplacement of the center of the baffle, control gas delivery to theshowerhead, pedestal/substrate support movement, vacuum port suction toevacuate gas from the reactor, power and frequency to the plasmaelectrodes, and/or heating and cooling elements, if present in aparticular implementation.

There will typically be a user interface associated with the systemcontroller. The user interface may include a display screen, graphicalsoftware displays of the apparatus and/or process conditions, and userinput devices such as pointing devices, keyboards, touch screens,microphones, etc. The system controller may be connected to any or allof the components shown in of a tool or module, including those shown inthe Figures of this application; the system controller's placement andconnectivity may vary based on the particular implementation.

In certain implementations, the system controller controls the pressurein various processing chambers in a tool. The system controller may alsocontrol the concentration of various process gases in the chamber byregulating valves, liquid delivery controllers, and MFCs in the deliverysystem as well as flow restriction valves in an exhaust line. The systemcontroller executes system control software including sets ofinstructions for controlling the timing, flow rates of gases andliquids, chamber pressure, chamber/showerhead/pedestal/substratetemperature, and/or other parameters of a particular process. Othercomputer programs stored on memory devices associated with thecontroller may be employed in some implementations. In certainimplementations, the system controller controls the transfer of asubstrate into and out of the various apparatuses shown in the figures.

The computer program code for controlling the processes in a processsequence can be written in any conventional computer readableprogramming language: for example, assembly language, C, C++, Pascal,Fortran or others. Compiled object code or script is executed by theprocessor to perform the tasks identified in the program. The systemsoftware may be designed or configured in many different ways. Forexample, various chamber component subroutines or control objects may bewritten to control operation of the chamber components necessary tocarry out the described processes. Examples of programs or sections ofprograms for this purpose include process gas control code, pressurecontrol code, and plasma control code.

The controller parameters relate to process conditions such as, forexample, timing of each operation, pressure inside the chamber,substrate temperature, process gas flow rates, RF power, as well asothers described above. These parameters are provided to the user in theform of a recipe, and may be entered utilizing the user interface.Signals for monitoring the process may be provided by analog and/ordigital input connections of the system controller. The signals forcontrolling the process are output on the analog and digital outputconnections of the apparatus.

Although several implementations of this invention have been describedin detail herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to these preciseimplementations, and that various changes and modifications may beeffected therein by one skilled in the art without departing from thescope of spirit of the invention as defined in the appended claims.

1. A baffle for a showerhead of a semiconductor processing tool, thebaffle configured for mounting within the showerhead such that a lowerplenum volume is formed between a bottom surface of the baffle and afaceplate of the showerhead and a upper plenum volume is formed betweena top surface of the baffle and an interior surface of the showerheadand such that gas introduced into the upper plenum volume duringsemiconductor processing operations flows through the baffle, into thelower plenum volume, and then through gas distribution holes in thefaceplate and towards a semiconductor substrate subject to thesemiconductor processing operations, the baffle comprising: a plate, theplate substantially axially symmetric about a center axis of the baffle,one side of the plate forming the bottom surface of the baffle, thebottom surface non-parallel to a reference plane normal to the centeraxis in a region of the plate defining the lower plenum volume; and aplurality of through-holes arranged in a radial array, the radial arraycentered on the center axis.
 2. The baffle of claim 1, wherein thebottom surface of the plate defines a conical frustum with a cone angleof between 170 and 179.9 degrees.
 3. The baffle of claim 2, wherein theradial array has a diameter of approximately half of the diameter of theplate.
 4. The baffle of claim 1, wherein the plate includes a lineardisplacement mechanism interface feature configured to interface with amovable end of a linear displacement mechanism.
 5. The baffle of claim4, wherein the linear displacement mechanism interface feature is acenter post, the center post centered on the center axis and protrudingfrom a side of the plate opposite the bottom surface and in a directionaway from the bottom surface.
 6. The baffle of claim 1, wherein thebaffle is made from aluminum.
 7. The baffle of claim 1, wherein thebaffle is made from a polymeric material.
 8. A showerhead for use in asemiconductor processing tool, the showerhead comprising: a faceplate,the faceplate including a faceplate bottom surface and a faceplate topsurface opposite the faceplate bottom surface, the faceplate top surfacepartially defining a lower plenum volume within the showerhead, whereinthe showerhead is configured to, when the showerhead is used in asemiconductor manufacturing process, orient the faceplate bottom surfaceto face a semiconductor substrate subject to the semiconductormanufacturing process; a baffle, the baffle including: a plate with asubstantially axially-symmetric shape about a center axis substantiallynormal to the faceplate, the plate having a baffle bottom surface facingthe faceplate and a baffle top surface facing away from the bafflebottom surface, wherein the baffle bottom surface further defines thelower plenum volume and the baffle top surface partially defines a upperplenum volume, and a plurality of through-holes arranged in a radialarray, the radial array centered on the center axis.
 9. The showerheadof claim 8, the showerhead further comprising: a linear displacementmechanism configured to displace a center region of the plate by a firstdistance along the center axis while an edge region of the plate issubstantially fixed with respect to motion along the center axis. 10.The showerhead of claim 9, wherein the linear displacement mechanism isa computer-controlled linear actuator or screw drive.
 11. The showerheadof claim 9, wherein the linear displacement mechanism includes athreaded rod configured to be manually rotated.
 12. The showerhead ofclaim 9, further comprising a center post, the center post centered onthe center axis and protruding from the baffle top surface.
 13. Theshowerhead of claim 12, wherein the center post protrudes through a sealin a back face of the showerhead, the seal configured to permit slidingmotion of the center post along the center axis with respect to theseal.
 14. The showerhead of claim 13, the showerhead further comprising:a linear displacement mechanism configured to displace a center regionof the plate by a first distance along the center axis while an edgeregion of the plate is substantially fixed with respect to motion alongthe center axis, the linear displacement mechanism fluidicly isolatedfrom the lower plenum volume and the upper plenum volume by the seal.15. The showerhead of claim 8, wherein the baffle bottom surface definesa conical frustum with a cone angle of between 170 and 179.9 degrees.16. The showerhead of claim 8, wherein the radial array has a diameterof approximately half of the diameter of the plate.
 17. The showerheadof claim 9, wherein: a first radial flow conductance between thefaceplate and the baffle exists when the plate is in an undisplacedstate, a second radial flow conductance between the faceplate and thebaffle exists when the plate is displaced by the first distance from theundisplaced state, and the second radial flow conductance exhibits lessradial flow conductance towards the center axis than the first radialflow conductance.
 18. A showerhead for use in a semiconductor processingtool, the showerhead comprising: a faceplate, the faceplate including afaceplate top surface partially defining a plenum volume of theshowerhead and a faceplate bottom surface configured to be facing asemiconductor substrate during a semiconductor processing operationperformed using the semiconductor processing tool; a plurality of gasdistribution holes distributed across the faceplate; and mechanicaldisplacement means for adjusting radial flow conductance across thefaceplate top surface.
 19. A showerhead for use in a semiconductorprocessing tool, the showerhead comprising: a faceplate, the faceplateincluding a faceplate top surface partially defining a plenum volume ofthe showerhead and a faceplate bottom surface configured to be facing asemiconductor substrate during a semiconductor processing operationperformed using the semiconductor processing tool; a plurality of gasdistribution holes distributed across the faceplate; and a baffle, thebaffle offset from the faceplate top surface, substantially centeredwith respect to the faceplate, and including: a baffle top surface, anda baffle bottom surface facing the faceplate top surface, wherein aseparation gap between the baffle bottom surface and the faceplate topsurface varies with respect to radial position such that the radial flowconductance between the faceplate top surface and the baffle bottomsurface varies with respect to radial position.
 20. A method forproviding a showerhead with a variable radial flow conductance, themethod comprising: introducing a process gas into a first plenum volumebetween a baffle within the showerhead and a faceplate of theshowerhead, wherein: the baffle includes a pattern of passages throughthe baffle through which the process gas is introduced into the firstplenum volume, the faceplate includes a pattern of gas distributionholes configured to deliver gas from the first plenum volume across thesurface of a semiconductor substrate, and the baffle is offset from thefaceplate and supported about the baffle's outer edge by the showerhead;displacing the center of the baffle to induce flexure of the baffle andto produce changes in separation distance between the baffle and thefaceplate that vary as a function of radial distance from a center axisof the faceplate.
 21. The method of claim 20, further comprising:determining the profile of the baffle when the baffle is displaced; andmanufacturing a new baffle that possesses the determined profile in anun-displaced state.
 22. A dual-plenum showerhead for use in asemiconductor processing tool, the showerhead comprising: a first gasfeed tube with a first interior volume and a first inlet configured tofeed gas to the first interior volume; a second gas feed tube, wherein:the first gas feed tube is concentric with the second gas feed tube,thereby creating an annular, second interior volume between the firstgas feed tube and the second gas feed tube, the second gas feed tube hasa second inlet configured to feed gas to the second interior volume, thefirst gas feed tube is of a smaller diameter than the second gas feedtube, and the first interior volume is fluidly isolated from the secondinterior volume within the second gas feed tube; and a dual plenumvolume substantially defined by an outer wall, the outer wallsubstantially axially symmetric about a first axis and the dual plenumvolume divided into an even number of sub-volumes by radial barrierssubstantially extending from the first gas feed tube to the outer wall,wherein: the first axis is substantially centered on the faceplate, abottom portion of the outer wall faces the faceplate, each sub-volumehas a plurality of plenum gas distribution holes passing through thebottom portion, every odd sub-volume is fluidly connected to the firstgas feed tube by a first radial passage, thereby forming a first plenumvolume, every even sub-volume is fluidly connected to the second gasfeed tube by a second radial passage, thereby forming a second plenumvolume, and the first plenum volume is fluidly isolated from the secondplenum volume between the plenum gas distribution holes and the firstinlet.
 23. The dual-plenum showerhead of claim 22, wherein thesub-volumes are all substantially the same size and overall shape. 24.The dual-plenum showerhead of claim 22, wherein the sub-volumes decreasein height along the first axis as a function of radial position withrespect to the first axis.
 25. The dual-plenum showerhead of claim 22,wherein the sub-volumes increase in height along the first axis as afunction of radial position with respect to the first axis.
 26. Thedual-plenum showerhead of claim 22, wherein there are at least 10sub-volumes.
 27. The dual-plenum showerhead of claim 22, furthercomprising a faceplate, wherein the faceplate includes a plurality ofgas distribution holes through the faceplate and is positioned such thatopenings of the gas distribution holes face the plenum gas distributionholes in the outer wall.
 28. The dual-plenum showerhead of claim 22,wherein the faceplate is offset from the outer wall by a gap.